Process of dyeing cellulose acetates



Patented m 21, 1925.

UNITED STATES RENE OLAVEL, '1 BASEL, SWITZERLAND.

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To. all whom it may concern: Be it known that I, Rnmi CLAvnL. a citizen of the Swiss Republic, of Basel, Sw1tzerland. have invented a certain new and 5 useful Improved Process of Dyemg Cellulose Acetates, of which the following 1s a specification.

This invention relates to the dyeing of cellulose acetates in artificial silk, film or any other form with vat dyes or sulphur dyes, the latter being likewise hereinafter in the claims included in the term vat dyes. In the specification of my U. S. Patent No. 1,448,432, it has been stated that cellulose acetates can be dyed direct with vat dyes when these contain active groups such as hydroxyl, amino, imino, imide or acidylamino groups.

vIn general, however the dyeingls WhlCh are obtained with vat dyes orsulp ur dyes in a dissolved or suspended form without any vatting, are of medium strength and seldom of very great depth.

An interest therefore attached to obtaining the darkest or fullest shades Withthese extremely fast classes of dyestuffs without the acetyl celluloses suffering or being affected in s mpath by the method of treatment as t e resu t of chemical reactions.

As is known, alkalies exert a partial or complete saponifying action upon cellulose acetates, e. g., cellulose acetate artificial silks,

so that the same are transformed or degraded into hydrocelluloses, whereby the physical properties, as for example tgloss, touch, etc., are unfavourably afl'ecte It has now been found that acetyl cellulose, whether in thread, filament, fibre, or other form, can be dyed in full and deep shades 40 with any vat or sulphur dyestulfs by adding to or employing in the vat or solution of the vat and sulphur dyestuifs, onl so much alkali that any saponification o the acetyl cellulose in the dyebath is excluded.

Further, there are preferably added to the dyebaths, in order to increase the dyeing power, relativel large quantities of water-soluble salts, or example chlorides, such as calcium chloride, ma esium chloride or barium chloride, an in order to Application filed October 5, 1922. Serial 170. 592,608.

prevent reci itations or separations that might ta e pace, one preferably employs protective colloids such as boiled oif liquor, gelatine, glucose, starch, etc.

Ewample 1.

1 kg. of bromindigo is made into a paste w1th 3 litres of hot water. Then 200 cc. of 32 B. caustic soda solution are added, and one reduces with 300 gms. of hydrosulphite 00 powder, added little by little.

About half a litre of the above stock solutlon is required for the! dyeing of 1 kg. of cellulose acetate silk. For this pu ose, therefore, about alf a litre of the stoc so- 66 lutlon is intro ed into a'bath of 25-30 litres, and 1 k of acetate silk is dyed in the bath at 5 C. for 4 hour with addition of 15-30 cc. of concentrated ammoma, 30 grams gelatine, and 100 grams mag- 10 nesium chloride.

The goods are then rinsed in water contammg acetic acid and are oxidized with a solution of 2% perborate and 4% acetic" acid of per cent strength for hour at N 60 C. The goods are subsequently rinsed, soaped and brightened.

The goods may, however, be sus ended in the air after dyeing and the oxi ation be finished 1n the above mentioned oxidizing so bath for the complete development.

- into a paste with 3 litres of hot water, add- 86 ing 200 cc. of 32 B, caustic soda solution and 300 gms. hydrosulphite wder. This stock solution is employed as ollows.

1 kg. of cellulose acetate silk is dyed for hour at 50-7 5 C. in one bath oontainin half a litre of the stock solution diluted wit 25-30 litres of water, 15-30 cc. concentrated ammonia, 3 litres boiled 01f liquor, and

.gms. sodium chloride being added.

The goods, after. dyeing, are wrun out or centrifuged, suspended in the air an subsequently, for complete oxidation, developed 'witha 2% solution of sodium. bichromate and 4% acetic acid of 60 per cent strength,

all calculated on the weight of the goods.

soaped The oods are then rinsed with Water,

and brightened.

What I claim and desire to secure by Letters Patent is 1. Process for dyeing cellulose acetate with vat dyes, characterized in that a vat is employed of such low alkalinity as is incapable of effecting any saponification of the cellulose acetate, said vat also containing protective colloid.

2. Process for dyeing cellulose acetate with vat dyes, characterized in that a vat is employed of such low alkalinity as is incapable of eifecting any sapmiiiication of the cellulose acetate, said vat also containing at least one water solublesalt.

3. Process for dyeing cellulose acetate with vat d es, characterized in that a vat is em loye of such low alkalinity as is incapable of cfiecting any saponification of the cellulose acetate, said vat also containing protective colloid and at least one Water soluble salt.

4. Process for dyeing cellulose acetate with vat dyes, wherein the dyeing is effected in a hydrosulphite vat kept weakly alkaline by ammonia, caustic alkali being present 1,54a9ee only in sufiicient quantity to form the leuco compound.

5. vProcess for dyeing cellulose acetate with vat dyes, wherein the dyeing is effected in a hydrosulphite vat kept weakly alkaline by ammonia, caustic alkali being present only in sufficient quantity to form the leuco compound, said vat also containing protective colloid.

6. Process for dyeing cellulose acetafe with vat dyes, wherein the dyeing is effected in a hydrosulphite vat kept Weakly alkaline by ammonia, caustic alkali being present only in suliicicnt quantity to form the leuco compound, said vat also containing at least one water soluble salt.

7. Process for dyeing cellulose acetate with vat dyes, wherein the dyein is effected in a hydrosulphite vat kept Wea 1y alkaline by ammonia, caustic alkali being present only in suflicient quantity to form the leuco compound, said vat also containing protectiiie colloid and at least one water soluble sa t.

In testimony whereof I have hereunto subscribed my name.

DR. RENE CLAVEL. 

